1. Field of the Invention
The present invention relates in general to an image-forming apparatus, and more particularly to an image-forming apparatus arranged to be capable of performing a so-called “non-margin recording operation”, namely, an operation to record an image, without a margin left along an edge of a recording medium (e.g., a sheet of paper), for example, to record an image over an entire length of the recording medium, without top and bottom margins being left on a recording surface of the recording medium,
2. Discussion of Related Art
In a conventional printer of ink-jet type, a recording head has a nozzle surface in which ink-ejecting nozzles are open, and is mounted on a carriage reciprocable in a main scanning direction, such that the nozzle surface faces downwards. When a recording operation is performed on a recording medium (e.g., a sheet of paper) by the recording head, the recording medium is intermittently fed or advanced by a predetermined incremental distance in a secondary scanning direction perpendicular to the main scanning direction. The recording medium being fed is supported by and moved on a platen disposed below the nozzle surface of the recording head, while an image is recorded on an upper recording surface of the recording medium, with droplets of ink ejected from the nozzles of the recording head.
When the so-called “non-margin” recording operation is performed without the top and bottom margins left along the leading and trailing edges of a recording medium, the ejection of the ink from the nozzles is initiated shortly before the leading edge of the recording medium has reached the downstream end of a predetermined effective recording area set in the printer, in the feeding direction of the recording medium, and is terminated shortly after the trailing edge has reached the upstream end of the effective recording area. The effective recording area is substantially opposed to the nozzle surface of the recording head in which the nozzles used for recording an image are formed and located, and has an effective recording length (as seen in the medium feeding direction) over which the ink droplets ejected from the nozzles are received or deposited. In this non-margin recording operation, therefore, the ink droplets may be deposited on-areas of the upper surface of the platen which are ahead of the leading edge of the recording medium and behind the trailing edge, as seen in the medium feeding direction. The ink droplets deposited on the platen cause a problem of contamination of the back or lower surface of the following recording media when these media are slidably moved on the platen.
JP-2000-118058A discloses an example of a solution to overcome the above-indicated problem, by forming the platen so as to have an upstream wall and a downstream wall which extend upright and in the main scanning direction and which are located on the respective upstream and downstream sides of the image-recording area of the printer and spaced apart from each other in the feeding direction of the recording medium such that those upstream and downstream upright walls partially define therebetween a container which is open upwards and in which an ink absorber for absorbing the ink droplets is accommodated. The upstream and downstream walls have respective rows of ribs formed on their upper end faces. See FIGS. 3, 4A, 4B and 4C of the above-identified publication JP-2000-118058A.
According to the solution disclosed in the above-identified publication, however, the ink absorbing material must be accommodated in the container of the platen such that the upper surface of the ink absorber is not located above the level of the upper ends of the ribs, to avoid a contact of the upper surface of the ink absorber with the recording medium being fed in sliding contact with the upper ends of the ribs. To assure a high degree of freedom of the recording medium from its contact with the ink absorber, the ink absorber must be accurately dimensioned and carefully installed within the container, undesirably requiring a high cost of manufacture of the ink absorber and time-consuming installation of the ink absorber in the container.
For effective absorption of the ink droplets by the ink absorber, on the other hand, it is necessary to form the platen with a sufficiently large area of opening of the container, so that the spacing distance between the upstream and downstream walls in the feeding direction of the recording medium is inevitably made large. The large spacing distance tends to cause the leading and trailing end portions of the recording medium to fall or deflect downwards and contact with the upper surface of the ink absorber in the container, if the recording medium has a relatively small thickness or a relatively low degree of stiffness, after the leading and trailing edges of the recording medium have passed the respective upstream and downstream walls of the container, with the recording medium being supported in a cantilever fashion at its leading and trailing end portions by the ribs of the upstream and downstream walls. Accordingly, the back surface of the recording medium may be contaminated with the ink at its leading and trailing end portions.
The non-margin recording operation has another drawback that the ink droplets ejected outside the recording medium cause an ink mist that also undesirably contaminates the recording medium, particularly, its back surface. In this respect, it is noted that a recent demand for a high resolution of image reproduction requires size reduction of the ink droplets, which leads to easier generation of the ink mist. Thus, there has been a need of assuring a high quality recording operation with a high image resolution while preventing the contamination of the recording medium with the ink.